This invention relates generally to film strip projectors and more particularly to improvements in film strip projectors which are adapted for use with tapes which have recorded thereon audio messages which pertain to the visual content of the film.
Film strip projectors are widely used in the instructional field as well as in sales promotion and other fields. This media is especially suitable for such purposes in that it permits the presentation of selected illustrations for varying time periods depending upon their informational content and thus conserves the amount of film required. It will be appreciated that the simultaneous performance of a synchronized audio message greatly increases the interest and usefulness of the visual presentation.
The illustrated embodiment is particularly suited for the projection of 35mm film but lends itself to other sizes as well. However, a particular characteristic of 35mm film strip is that the development standards are not well formulated throughout the industry. In this respect, sprocket holes which are used for driving the film in the camera and in the projector are not consistently located at a predetermined spacing with respect to the individual frames or images on the film strip. This characteristic prevents the indexing of the film frames within a projector aperture by means of a simple original sprocket hole orientation. Therefore initial framing alignment must be manually accomplished. The film sprocket holes on a particular film strip are precisely located relative to the position of all of the film frames on that particular strip and therefore the film drive mechanism must be extremely accurate to insure consistent framing of the respective frames throughout the entire roll of film once initial framing is achieved.
A particular feature of the illustrated embodiment herein is the inclusion of a modified tape recorder which supplies audio messages related to the visual images being projected, as well as supplying control signals to the projector for automatically advancing the film strip, frame by frame, in synchronization with the audio format.
An object of the present invention is to provide a new and improved Geneva type mechanism which can be successively indexed and still maintain an accurate relative position without requiring the complexity and relative high cost of previous such devices.
Another object of the present invention is to provide a Geneva type drive mechanism which is particularly suited for 90.degree. rotational indexing for use within a film strip projector.